Metal Sonic is a misnomer, as he is actually made of plastic.

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Metal Sonic is a misnomer, as he is actually made of plastic.
Sonic Blast on Game Gear is derided and forgotten at Sega because Sonic goes through a pipe in that game, which upset the higher-ups when they found out the game had pipes.
Some copies of Super Smash Bros. Melee accidentally shipped with the game disc for Sonic Adventure 2: Battle. Affected purchasers were delighted to receive the superior game instead of what they ordered.
Spindashing was removed from the original Sonic the Hedgehog because the resulting sonic boom shattered the TVs used for testing.